The present invention relates to the field of seismic and expansion joint covers.
Expansion and seismic joint covers are, essentially, covers or mechanism devices to cover expansion and seismic joints to provide pedestrian or vehicular passage over a joint, and provide a smooth transition from one slab to another, while not inhibiting joint movement or restricting this movement as a result of the mechanism employed. Generally, the mechanisms employed to position the expansion/seismic joint cover over the joint are either of a mechanical nature or make use of an elastic and recoverable element to provide the impetus (spring-memory or return-force) to maintain the joint cover in a median position relative to the joint movements occurring. These movements may be experienced in all three planes, such as expansion and contraction, deflection and shear of the joint.
Various mechanisms are thus employed to deal with this three directional movement and the mechanism to stabilize the expansion joint cover and restore it into a xe2x80x9cneutral positionxe2x80x9d relative to the movement that has taken place.
FIG. 1 is a typical prior art expansion/seismic joint cover manufactured by Migua Fugensysteme GmbH and CO. KG, in Germany particularly for Seismic Joints. As can be seen, this has a cover plate extending across the width of the joint to allow for both vehicular and pedestrian traffic. As a self-centring mechanism, it utilizes the recovery ability of elastomeric extrusions. These extrusions exert the return force required to reposition the cover plate as a result of movements occurring in the joint. The dotted line, seen midway through the joint, is a horizontal bar set across the width of the joint to act as a stabilizing element for the elastomeric extrusions in the centre. It is there to add stability to the joint and allow the central (metallic) part of the joint to be fastened to the cover plate, prior to its (the horizontal bar) removal. This expansion/seismic joint cover is intended to be watertight. The waterproofing is confined substantially to the upper surfaces of the joint immediately below the cover plate. However, once the horizontal (stabilizing) bar is removed, remedial work on the joint is difficult as removal of the cover plate will allow the central portion of the joint to collapse as it is no longer supported (by the horizontal bar).
FIG. 2 shows an expansion/seismic joint made by Watson Bowman Acme Corp., in the U.S.A. In this design, the cover plate is attached to a scissors-type mechanical device immediately below it. The scissors-type mechanism is similar to a xe2x80x9cpantographxe2x80x9d or expanding scissors type hot-plate mat. In other words, a scissors-type movement contained between nylon bearings and running the length of the joint. In this type of mechanism, an increase or decreases in the joint width will result in the repositioning of the cover plate along the centre line. However, this expansion/seismic joint cover is not watertight immediately below the cover platexe2x80x94as is the case with the expansion/seismic joint cover in FIG. 1. Thus, an elaborate system of gutters attempts to provide a solution to the watertight issue. The joint, in effect, suffers from three major problems. Firstly, an inability to inspect and clean out the joint other than by removal of the whole joint assembly (the scissors mechanism prevents direct access into the joint below the cover or slide plate). Secondly, the ingress of waterborne salts into the joint will seriously affect the long term performance of the self-centring mechanism. Thirdly, the joint design lacks xe2x80x9cwatertight propertiesxe2x80x9d.
The above prior art illustrates two objects of the present invention. The first is that the cover plate should be removable to permit inspection of the joint below. The second object is that the joint should be watertight at, or immediately below, the line of waterproofing that is applied to the deck. This will ensure a waterproofing line of integrity across both decks, on either side of the joint, and through the actual joint itself.
It can be seen from FIGS. 1 and 2 that the emphasis, until this point in time, has been to utilize either a mechanical mechanism or elastomeric extruded profile as the correcting or centring element required to maintain the cover plate in its correct position relative to joint movement occurring beneath it. In other words, the cover plate cannot be allowed to merely sit on the surface of the joint but must be guided to maintain a central position or neutral position relative to the joint movement occurring.
In the present invention, the use of an impregnated foam sealant as an elastic recovery or return force mechanism has the dual advantage that the system can remain watertight immediately below the level of the cover plate while at the same time the impregnated foam sealant acts as the return force or stabilizing element for the cover plate.
In the present invention, then, relates to a seismic/expansion joint seal and cover comprising a cover plate, a central spine extending downwardly from said cover plate, and at least one layer of a resilient compressible foam sealant on each side of said spine.